Insight into Risk Factors for Pulmonary Hypertension in Thalassemia: Abnormal Platelet, Hemolysis and Vascular Markers.

Pulmonary hypertension (PAH), determined on echocardiogram by a tricuspid jet velocity (TJV)≥2.5m/sec in the absence of diastolic dysfunction is a common complication in patients with beta-thalassemia intermedia (TI) and some patients with thalassemia major (TM). The pathogenesis is thought to be multifactorial, primarily due to increased hemolysis, hypoxia, endothelial proliferation and thrombosis. Identifying biomarkers of these risk factors could increase understanding of the pathogenesis and facilitate screening and risk stratification in these patients. A cohort of 44 patients (mean age 29±11 years; TM-29; TI-15) was screened by echocardiogram for presence of PAH and evaluated by the following lab measures: Markers of platelet activation (P- selectin, soluble CD40 [sCD40L]); thrombin generation (thrombin-anti-thrombin [TAT]; prothrombin fragment 1+2 [F1.2]); increased ventricular pressure strain (brain natriuretic peptide [BNP]) indicating; and plasma free Hb, indirect bilirubin, LDH and NOx, for hemolytic activity. 14 patients had PAH, indicated by increase in TJV (range 2.5–3.1, mean 2.63±0.1 m/sec) and 30 patients had no PAH. 8/14 (57%) with PAH had prior splenectomy versus 6/30 (20%). 4/14 (28%) with PAH and 5/30 (16%) without PAH were non-transfused TI patients. 10/14 PAH patients had a mild increase in TJV (2.5–2.7m/sec) while 4/14 had a moderate increase in TJV (2.7–3.1m/sec). These 4 patients were splenectomized, 3 non transfused TI and one started transfusions only in adulthood. Results demonstrated an increase in P selectin which correlated with the severity of TJV: 52.4±14ng/ml in mild PAH, 60±18 ng/ml in moderate cases and 38±15 ng/ml in the PAH(−) group (R= 0.5 p<0.008). A similar trend in sCD40L was noted: 6.4±4 ng/ml in mild PAH, 7.8±2.7 ng/ml in moderate severity (R= 0.9, p<0.05) and 4.0 ± 0.7 ng/ml in patients without increase in TJV. Mean TAT and F1.2 were not helpful in distinguishing PAH(+) and PAH (−) patients. There was a trend of increased hemolysis as indicated by higher bilirubin levels and plasma free Hb: Bilirubin was 2.2±1.2, 3.2±2.1 and 1.8±0.9 mg/dL in patients with mild, moderate elevated and normal TJV, respectively. (R=0.3 p<0.04). Plasma free Hb was elevated in 35/44 patients but to a higher extent in 4 patients with a higher TJV; mean 120±180 vs 70±110mg/ml in the remaining 40 patients (nl<15). LDH was comparable in all groups. Reduced NOx levels were noted: 6.7±4.3 in mild cases, 4.7±1.9 in moderate cases and 10±16 in patients without indication of PAH. BNP levels were normal in all patients. Elevated adhesion molecules were mostly seen in patients with higher liver iron concentration suggesting further contribution of iron overload to the inflammatory stress and endothelial disruption. sVCAM-1, sICAM-1 were 890±700 ng/ml, 220±160 ng/ml, respectively in patients with PAH, and 454±200 ng/ml, 151±120 ng/ml respectively in those with no detected PAH. (p=0.05 for sVCAM, ns for sICAM). These preliminary studies demonstrate an association of platelet activation, hemolysis, vascular inflammation and PAH, providing insight into the pathogenesis. The identified biomarkers might serve for monitoring of increasing pulmonary pressure and need for intervention, in particular in non transfused TI patients.